Alternating-current machine.



No. 857,953. PATENTED JUNE 25, 1907 R. D. MBRSHON. ALTERNATING CURRENT MACHINE.

APPLICATION FILED JULY5,1904.-

No. 557,953. PATBNTBD JUNE 25, 1907. N. N'MERSHON. ALTENNATING CURRENT MACHINE.

APPLICATlON FILED JULY5,19O4,l

4 SHEETS-SHEET 2.`

Wiflnesse:

2 4 /3 Q Imaz/ibi PATENTED JUNE 25, 1907.

R'. ALTBRNATING CURRENT MACHINE.

D. MERSHDNl APPLlUATION FILED JULY5,1904.

4 SHEETS-SHBET S.

PATENTED JUNE 25.1907.

R. D. MERSHON.

ALTERNATNG GU'RRENT MGHINE.

APPLICATION FILED JULY5,1904.

SH 'lS-SHEET 4.

'actances and capacities, as well' as such -for running conditions.

1U Nrrnn `fsfraii" liloH 852%53. tipeciicaton or te sters Essent.

pplication filed July 5, i964-, Serial lio. 215,238.

m atZZ whom, i? imty concern:

Be' it known that l", Reigen Ministros, a citizen et the United States, residing at New York, in thefconnty and State of New "forli, have invented certain new and useful inn proveniente in Alternating- Current itis cliines'of which the following is specifica tion, reference being had to the drawings ac companying'and forming part the saine.

My invention relates to alt-ernating` current machines, both generators and inotors, which are adapted to have the number oi their poles varied, .and has tor its` object to provide means for lintroducing into the secondary element devices which by then1 effect modify the operation ot' the machine.l Among such devices may be mentioned resistances, re-

otlier devices as may lend themselves to such uses. My invention therefore does not reside inthe broad combination of these devices therewith, but rather in the provision oi such connections for these devicesthat they are effectively utilized at lthe times when their eiiects are desired.

As is Well known, inthe case of an induction-motor, for example, better results are obtained in starting the motor if there is introduced into the secondary a resistance, which is cut out as the motor cornes up to speed. But in order to Obtain this riieostatic control, which involves switching or the equivalent, it has beennecessary to employ slip rings on one element of the motor, or to have a conimutating switch in therotating secondary, operated by a `rod or lever, or by devices actuated by centrifugal force. it has therefore been proposed to use a perinanent resistance, in the secondary, which compromise between the best starting resistev ance, and the lowest resistance which is best rlhis plan also possesses obvious disadvantages.

in my invention, however, employed with machines in which the number of poles is varied,r a high resistance or any other suitable device may be used in starting, in running' at ioW speeds,'but will have no detrimental etlect on the operation of vthe motor when the O7:

speed thereof 1s increased and the number poles reduced. This ,result is attained by manner of connecting the resistance or other device with the secondary winding, the connections beine' so arranged that a given de vinci-vill be eitective ior one number poles, and non-eileetive or less eii'ective for ynunibers as desired, each set being ad)L nuin`f ers of poles. Several sets of ina-y used, over as wide a range poles, and so connected with the second vinding or windings that for each number of" wies there will be eiiective in the secondary,

device, or oi dc vices, .vhich is suited o adfusted for sucli number ol' poles. llso, 'the connections for the respective devices, or thereof, are such that those eil'ective gliel* number of poles become ineiiective or less eil'ective lor succeeding lesser ouinbers. in other Words the devices are cut in or out, it were, in succession the dit" rent numbers of poles are produced in the "ori44 mary, and this cutting in or out is not caused by tiie actuation of any mechanical parts in the secondary circuits, but resultsy entirely 'from the nature oi the connections between the devices and the secondary windings he invention therefore possesses none of the disadvantages inherent in collector rings, or in coininutating switches, etc., which have heretofore been employed lior analogous purposes, in cases Where the device is small or proportioned for a particular nuii'ibei.oif

.enough to be included in the secondary element. lhen the device or devices are 'of 'suoli nature that they cannot be so included,

slip rings or similar instrunientalitics 'will have toloe used but in suoli case, as also in the case of a stationary seconda v, the use of any iorm of switch for cuttingthe modifying devices in or out is rendered unnecessary.

My invention will be iuoro readily understood When explained in connection uit li the accompanying' drawings. ln explaining the principle oit' the invention, single phase ina- -cliines with salient poles and rinnl wound secondaries are shown, for the salie oi clearness, and in these iigures no means 'lor varying the number oi" poles is illustrated, that eil'ect, for purposes of explanation, being' secin'ed by the use of di'l'lferent priniaries. in other iigures, however, the machine is sliovn as a single phase one adapted va` 'ria'ion in the number of its poles, the niet/nod chown loc-iin;- that oi leading currents in at tbe proper points in the primary winding.

it will be understood that tlic invention is applicable to motors or generators oi any other typo, both single and polyphasl and with'uniformly or non-unitornily distributed windings Whether ol" the ringl or drum ype. lt also immaterial whether tho dil'oront cors or giclee all produced by the IOO Si CJ same winding, or by different windings or combinations of windings, in both primary and secondary elements. is a matter ol" in practice the best results will be obtained with distributed windings, where the different numbers oi poles are produced by vditl'ereiit windings, or by leading in 'the currents at the proper points in the same winding.

in the drawings, Figure l shows diagraminatically a two pole motor, having a ring secondary snort circuited across one diameter, Fig. shows a four pole motor with the same secondary. F 3 shows a four pole motor, having its secondary short circuited across four electrical diameters; i?

lsliows an eight pole motor., with tiie secondary illustrated in the oreceding -figure. 5 is av dir fram illusl `ti g my invention ap- C plied to motor adapted to be run with tiro or tour Apoles.

the same. two, iour, inf i diagrauiniatically ement for Fig. illustrates .l or squirrel-cage secondary embodying my invr-zntion, -with a high resistance i'or tour poles and low refer two poles. 9 ilh, `tes diagrammatically s ic niotor. with i invention eiiiilioi foin, and capable poles. Figs. l() and l l, illustrate diagrama s tically secondary elements in which both resistances and condensers are used for one number oiE polen, the condenser and. resistance being in mul-- tiple in Fig. l0 and iii series in Fig. 11.

'llhroughout the various iigures of the drawings A designates the motor primary.

and. ld the motor secondary, wherever these elements apnea eferring now to Fig. i, the magnetic ihn; from pole to pole through the secondary winding is indicated by the dotted lines. Across the diameter oi" the secondary is a short circuit, l, which in the position shown is effective to its fullest extent. in any other position it is less eiliective, but there may be any number of diametrical short circuits so' that in any position the secondary will be eiiectively short circuited. But if the secondary ot Fig. l be nut in the field or' Fig. 2, which has tour poles, it is not short circuited for the ihn; ot the latter field, as will be seen from an inspection o1" the figure, which the tluir relation to the conductor may be iioted. In order to have a short circuit e'll'ect with four poles in the primary or, in tact, with any number of poles, the short circuits must be across electrical diameters, as at la in Fig. 3, or across chords lessthan the electrical diameter. F rom the explanation before given in connection with Figs. 1 and 2, it will be seen that an elliective short v circuit of in every position may be obsenses this secondary in the lield ol" Fig. 4, which has eight poles, there is again no short circuit effect; and to produce this ell'ect it is necesary to place the short circuits across electrical diameters of one-eighth the circumference. It is seen, therefore, that short circuits across electrical diameters in. Fig. l are not effective in F ig. 2 and that those which are ei'lective in Fig. 3 are not el'lective in Fig. 4;. The converse, however, is not true, for short circuit across electrical diameters in Fig. l are effective in Fig. 3 and aree'li'ective also in Figs.' 2 and 1. That the short cir-- cuit across the electrical diameter' for the lower number of poles is not ell'ective for the higher number, but the short circuit across the electrical diameter or a higher number ot poles is etiective 'jor a lower number.

Keeping the above in mind, suppose that when the motor running at greater iiuiiiber o1" poles it is (liesirable to have in the secci'idary circuits resistaiices, for example. These resistaiices may be inserted iii the short circuit paths across the electrical diameters for the greater number ot polos and they will then be ine'iective for tho lesser number of poles because when the motor is operating at "ie lesser number or poles thc resistances are, in eilect, shunted by a 'path ol' no resistance-ma short circuit path. ln this case, ther/etere, not only are the short circuits for the le ser number oi poles iiicllcctivc for the greater number of poles but also the resistances for the greater number ot polos are ineffective or practically so for the lesser number of poles.

in general, suppose the machine is to be capable of operation at two' or more numbers ot poles and that l'or each number ot poles there is to be in the secondary an eilect equivalent to that of certain resistances'the value of the certainresistanoes to be less as the pole numbers are diminished. The resistances across electrical diameters for the greatest number ci' poles are those ctlectivc for that number of poles. The equivalent eilective resistance for the next lower number of poles will be one -iifliose value lies between that for the greatest number of poles and that due to the resistances across the electrical diameters of the lower number of poles and will be controlled by the value ol' the latter resistance. ance for the next lower number olE poles wi ll be one lying between the e'fl'ective resistance for the preceding number and that across the electrical diameter tor the next lower number and controlled by it and so on down to, if desirable, a 'number of poles whose electrical diameters are short circuited. In this case therefore each number of poles may have certain definite e'ifective resistances effective for that number of poles and 'for none ofthe other pole numbers employed. The same explanation applies to other devices than gle- 'The equivalent resistlIO ISO

sistances whether the devices be all of the same nature or not. This will be clearly seen from Fig. 5. This ligure shows a single phase motor provided with leads m, en', m m by which it may be run at two poles or at four. Y y

C indicates a diagrammatic controller connecting the motor with the single phase source D. By tracing the connections it will be seen that in the first position of the controller leads m, m. will lie-connected with the source, producing two poles. In the second position all the leads are connected with the source, producing four poles. The secondary, B, in a two pole primary, is shown with resistances in the four pole short circuits, and none in the two pole short circuits.

As previously explained, in a case like Fig. 5 there would be a greater number of two pole and four pole paths than are shown, the others being omitted from the diagram to avoid complicating the iigures. As shown in Fi?. 5 there are two shortV circuits for the two pol condition, 90 degrees apart, while the four pole conductors or paths are 180 electrical degrees apart, considered from the standpoint ot four poles. In practice there would prol'iahly be, for the greatest number of poles, at least Atwo sets of paths, lin quadrature; and there might be others at other angles. rllhere are also i other connections which give an equivalent eilfect, and which are somewhat simpler than those just described. For example, as will be at once seen, the arrangement shown in F ig. 6, in.

VV`which theA resistance R is connected between the short-circuits 1h is the equivalent oi the connections shown in Fig.

As previously stated, any number ot sets of' devices may be used in the secondary. lin Fig'. 7 is shown diagrammatically a secondary for, a machine in -which the number of poles in the primary may he eight, four andY two. The resistances shown as included in the secondary circuits are insertedpn thel `.when the pole number is changed to lour the resistances r r become inactive or nearly so, when the pole number is two the resistances r fr become inactive or nearly so, especially if, will usually be the case the resistances "1' fr have as low a value as possible, that is,

constitute a short circuit. will be noted that the paths are 9G electrical degrees apart for the .eight pole connection,45 electrical degrees apart for the ,four pole, 22.5 electrical degrees apart for the two pole. in the latter case of course electrical. deg and degrees of arc are the saine. ln precw tice there might be many more patl .i are shown. y

As previously explained, the device to be used in the secondary may be a resistance, a reactance, or a capacity, etc. 'For example, if a properly constructed capacity be introduced into the secondary of an induction motor the torque of the motormay be enor mously increased. at low speeds, but .this torque will in general diminish rapidly as 'the speed of the motor, rises toward synchronism for that number otpoles to which the introduction of the condenser corresponds, because in approachingl this speed the vol tage and frequency impressed upon the condenser diminish.

ln Fig. 9 is shown a motor arraneed to op crate with two and With four poles with ren sistances R inthe secondary for the Itwo pole connection and condensers E i' or the four pole connection. ln this igure the motor is connected. with the single phase source D through a diagrammatic controller C and by tracing the connections it will be seen that in the first position orp the controller the leads m4 and 'mf will be connected with. the source, producing two poles, and in the next position all the leads, m4, 'm5, m6., m7 will be connected with the source, producing four poles. ll' the capacity of the condenser. be properly proportioned, on starting the motor with the four pole connection a strong torque will be produced, which will fall ofi' as the motor anpreaches synchronism for four poles. But when the torque has diminished to a point below that required the inotor maybe switched oil of the tour pole connection on to the two pole connection, which connection will then produce a higher torque than it would at starting, because the motor has increased in speed toward that at which the two pole connection. would give its highest torque. Or, instead oi a condenser alone, a condenser and resistance in parallel, or in series, might be used, as in Figs. l() and l1 respectively. In the case ol' usingI the condenser alone, and under some circumstances where the combination of condenser and resistance is used, the primary connections 'forfour poles may be retained even after the two pole connection has been made. `When connected in this 'way the two devices in the secondary will take currents which in general will be independent oi" each other, as will also their corresponding currents in the primary winding' or windings. ln consequence the resulting current delivered to the primary element by the supply circuit will be a resultant ot the two primary currents due to the secondary currents just mentioned. The same course may be res ed to with more than two numbers of poles, and also with any other devices or sets of devices whether the nature oi the devices for each number of poles be the saine or not.

Where a combinatifni of condenser and resistance is desirable an electrolytic con- TIO , adapted for variation lin the number of its the induction motor in that when driven above synchronous speed it Will act as a generator, the scheme described herein with particular reference to an induction motor applies equally well to induction generators.

What I claim is: 4 ,1. Inan alternating current macln'ne,

poles, thefcombinatio'n with the primary element, of a secondary element, devices or sets of devices in the secondary element for modifying or improving the operation of the machine with two or more numbers of poles, and permanent connections for said devices or sets of devices with the secondary winding or windings at such points that said devices or sets of devices become successively more effective in their action as vthe number of poles is increased, as set forth.

2. In an alternating current machine, adapted for variation in the number of its poles, the combination with -the primary element, of a secondary element, devices or sets of devices in the secondary element for modifying or improvingthe operation of the machine with two or more numbers of poles, and permanent connections from said devices or sets of devices tothe secondary winding or windings at such points, relative `to the number of poles, that said devi'ces or sets of devices become successively more effective in their action as the number of poles is increased, as set forth.

3. In an alternating current machine, adapted for variation in the number of its poles, the combination with the primary element, of a secondary element, devices or sets of devices in the secondary element for modifying or improving the operation of the machine, permanent connections from said Adevices or sets of devices to the secondary winding or windings, at such points that the said devices or sets of devices are less effective or non-effective in their action for one number of poles and more effective for a greater number of poles, additional devices or sets of devices-in the secondary element for modifying or improving the operation of the machine, Aand permanent connections therefrom to the secondary winding or windings at such points that said additional devices or sets of devices are less effective or non-effective for said greater number of poles and more effective for a still greater number of poles, as set forth.

4. In an alternating current machine, adapted for variation in the number of its poles, the combination with the primaryi'element, of a secondary element, devices or sets of devices in the secondary element' for modifying or improving the operation of the inachine, permanent connections from said devices or sets of devices to the secondary winding or windings, along electrical diinneA ters for one number of poles, additional devices or sets of devices in the secondaryele-- ment for modifying or improving the operation of the machine, and permanent connections therefrom to the secondary winding or windings along electrical diameters for another number of poles, as set forth.

5. In an alternating current machine, adapted for variation in the number of its poles, the combination with the primary element, of a secondary element, resistances in thesecondary element, and permanent connections for said resistances with. the secondary winding or windings at such poilus that said resistances become successively more effective in their action as the number of poles is increased, as, set forth..

6. In an alternating current machine, adapted for variation in the number of its poles, the combination with the primary element, of a secondary element, resistances in 4 the secondary element, permanent connections from said resistances to the secondary winding or windings at such points that the vsaid resistances are less effective or non-effective in their action for one number of poles` and more effective for a greater number of poles, additional resistances in the secondary element, and permanent connections therefrom to the secondary winding or windings at such points that said additional resistances are less effective or non-effective for said greater number of poles and more effective for a still greater number of poles, as set forth.

7. In an alternating current machine, adapted for variation in the number of its poles, the combination with the primary element, of a secondary element, resistances in the secondary element, and permanent connections from said resistances to the ondary winding or windings along,r electrical diameters for two or more numbers of poles, whereby said resistances become successively effective or more effective in their action as the number of poles is increased,

set forth.

8. In an alternating current machine, adapted for variation in the number of its poles, the combination with the 'primary element, of a secondary element, short circuits i in the secondary element along electrical diameters for the minimum number of "poles with which the machine is to be operated, devices in the secondary element for modifyingr or improving the operation of the min-,bine with-two or more numbers of poles, and permanent connections for said devices with the secondary winding?r or windings at such poiiits that said devices become effective or more effective in succession as the number of poles is increased, as set forth.

lio

IIC'

srs'zgee'ssl t 5 9'. In an alternating. current lfmachine, permanent connections therefor with the adapted for variation in the number of its secondary Winding or Windingsacross elec- 1c polcs'the combination with the primary eletrical diameters for the next smaller number ment, of a secondary element, devices or sets of of poles, as set forth.

5 devices in the secondary for modifying or im- RALPH D. MERSHON.

provngthe operation of the machine with Witnesses: fits maximum'number'o poles, additional de- M. LAWSON DYER,

vices or sets of devices in the secondary and S. S DUNHAM. 

